return only Digits 0-9 from a String

Question

I need a regular expression that I can use in VBScript and .NET that will return only the numbers that are found in a string.

For Example any of the following \"str

Answer 1

As an alternative to the main .Net solution, adapted from a similar question's answer:

string justNumbers = string.Concat(text.Where(char.IsDigit));

Answer 2

Have you gone through the phone nr category on regexlib. Seems like quite a few do what you need.

Answer 3

Note: you've only solved half the problem here.

For US phone numbers entered "in the wild", you may have:

• Phone numbers with or without the "1" prefix
• Phone numbers with or without the area code
• Phone numbers with extension numbers (if you blindly remove all non-digits, you'll miss the "x" or "Ext." or whatever also on the line).
• Possibly, numbers encoded with mnemonic letters (800-BUY-THIS or whatever)

You'll need to add some smarts to your code to conform the resulting list of digits to a single standard that you actually search against in your database.

Some simple things you could do to fix this:

• Before the RegEx removal of non-digits, see if there's an "x" in the string. If there is, chop everything off after it (will handle most versions of writing an extension number).

• For any number with 10+ digits beginning with a "1", chop off the 1. It's not part of the area code, US area codes start in the 2xx range.

• For any number still exceeding 10 digits, assume the remainder is an extension of some sort, and chop it off.

• Do your database search using an "ends-with" pattern search (SELECT * FROM mytable WHERE phonenumber LIKE 'blah%'). This will handle sitations (although with the possibility of error) where the area code is not provided, but your database has the number with the area code.

Answer 4

In respect to the points made by richardtallent, this code will handle most of your issues in respect to extension numbers, and the US country code (+1) being prepended.

Not the most elegant solution, but I had to quickly solve the problem so I could move on with what I'm doing.

I hope it helps someone.

 Public Shared Function JustNumbers(inputString As String) As String
        Dim outString As String = ""
        Dim nEnds As Integer = -1

        ' Cycle through and test the ASCII character code of each character in the string. Remove everything non-numeric except "x" (in the event an extension is in the string as follows):
        '    331-123-3451 extension 405  becomes 3311233451x405
        '    226-123-4567 ext 405        becomes 2261234567x405
        '    226-123-4567 x 405          becomes 2261234567x405
        For l = 1 To inputString.Length
            Dim tmp As String = Mid(inputString, l, 1)
            If (Asc(tmp) >= 48 And Asc(tmp) <= 57) Then
                outString &= tmp
            ElseIf Asc(tmp.ToLower) = 120
                outString &= tmp
                nEnds = l
            End If
        Next


        ' Remove the leading US country code 1 after doing some validation
        If outString.Length > 0 Then
            If Strings.Left(outString, 1) = "1" Then

                ' If the nEnds flag is still -1, that means no extension was added above, set it to the full length of the string
                ' otherwise, an extension number was detected, and that should be the nEnds (number ends) position.
                If nEnds = -1 Then nEnds = outString.Length

                ' We hit a 10+ digit phone number, this means an area code is prefixed; 
                ' Remove the trailing 1 in case someone put in the US country code
                ' This is technically safe, since there are no US area codes that start with a 1. The start digits are 2-9
                If nEnds > 10 Then
                    outString = Right(outString, outString.Length - 1)
                End If
            End If
        End If

        Debug.Print(inputString + "          : became : " + outString)

        Return outString
    End Function

Answer 5

The simplest solution, without a regular expression:

public string DigitsOnly(string s)
   {
     string res = "";
     for (int i = 0; i < s.Length; i++)
     {
       if (Char.IsDigit(s[i]))
        res += s[i];
     }
     return res;
   }

Answer 6

In .NET, you could extract just the digits from the string. Like this:

string justNumbers = new String(text.Where(Char.IsDigit).ToArray());